diff --git a/Gemfile b/Gemfile
index aece9be..375f5b7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,4 +22,4 @@ gem 'middleman-syntax', '~> 3.0.0'
 gem 'redcarpet', '~> 3.3.4'
 
 # For "summary"-Helper
-gem 'nokogiri', '~> 1.6.8'
+gem 'nokogiri', '~> 1.13.9'
diff --git a/Gemfile.lock b/Gemfile.lock
index 7134ed0..d56d141 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -88,10 +88,11 @@ GEM
     middleman-syntax (3.0.0)
       middleman-core (>= 3.2)
       rouge (~> 2.0)
-    mini_portile2 (2.1.0)
+    mini_portile2 (2.8.0)
     minitest (5.10.1)
-    nokogiri (1.6.8.1)
-      mini_portile2 (~> 2.1.0)
+    nokogiri (1.13.9)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     padrino-helpers (0.13.3.3)
       i18n (~> 0.6, >= 0.6.7)
       padrino-support (= 0.13.3.3)
@@ -100,6 +101,7 @@ GEM
       activesupport (>= 3.1)
     parallel (1.10.0)
     public_suffix (2.0.5)
+    racc (1.6.0)
     rack (2.0.1)
     rack-livereload (0.3.16)
       rack
@@ -131,7 +133,7 @@ DEPENDENCIES
   middleman-livereload
   middleman-sprockets (~> 4.0.0)
   middleman-syntax (~> 3.0.0)
-  nokogiri (~> 1.6.8)
+  nokogiri (~> 1.13.9)
   redcarpet (~> 3.3.4)
   tzinfo-data
   wdm (~> 0.1.1)